This is an excellent introduction to statistical mechanics. Pathria is a physicist and the topics covered have a definite physics flavor (Bose and Fermi systems), which chemical engineers or chemists may not find engaging. However, the introductory material on the theory of ensembles (chapters 1-4) is excellent, does not require special background in physics, and is presented from multiple perspectives that help clarify concepts. I recommend Pathria as one of the most lucidly written introductory texts on stat mech. The historical development of statistical physics (in the introduction) is an added bonus. I have used this book as a resource, not as a standalone text, but keep in mind that if you are trying to learn stat mech on your own, you should be prepared to work with multiple sources. (Review based on the first edition of the book, reprinted 1982.)